U.S. and Europe Retrospective Responsibility Plans - Changes in the U.S. Litigation Escrow Account (Detail) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2023	Sep. 30, 2022
Escrow Account [Roll Forward]
Balance at beginning of period	$ 1,449	$ 894
Deposits into the U.S. litigation escrow account	1,000	850
Balance at end of period	1,764	1,449
Interest Income \| Opt-out Merchants
Escrow Account [Roll Forward]
Payments to opt-out merchants, net of interest earned on escrow funds	$ (685)	$ (295)

Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 230
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-Topic 942
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